I. Okutsu et al., in an article entitled Endoscopic Management of Carpal Tunnel Syndrome, Arthroscopy, 5(1):11-18 (1989), described a subcutaneous endoscopic procedure for releasing the transverse carpal ligament that utilizes an endoscope inserted in a clear plastic tube to view the ligament, and a hooked retrograde knife to releasing the ligament. Okutsu et al. also described the use of an L-shaped probe to clear the synovial membrane from the transverse carpal ligament in order to facilitate viewing of the ligament.
Simultaneously with the report by Okutsu et al., James C. Y. Chow, M.D., in an article entitled Endoscopic Release of the Carpal Ligament: A New Technique for Carpal Tunnel Syndrome, Arthroscopy, 5(1): 19-24 (1989), reported an endoscopic technique for releasing the transverse carpal ligament using a hooked knife inserted in a slotted arthroscopy sheath. A follow-up article by Dr. Chow, entitled Endoscopic Release of the Carpal Ligament for Carpal Tunnel Syndrome: 22-Month Clinical Result, Arthroscopy, 6(4): 288-296 (1990), further describes the technique. A product brochure entitled A Breakthrough in Carpal Tunnel Release, published by Smith & Nephew Dyonics, Inc. of Andover, Mass. in 1990, illustrates the surgical instrument used in performing the technique described in Dr. Chow's journal articles. A second brochure entitled An Illustrated Guide to Endoscopic Release of the Carpal Ligament, published by Smith & Nephew Dyonics, Inc. of Andover, Mass. in 1991, describes the techniques in further detail and illustrates the instrument used in the procedure.
In Dr. Chow's technique, after access to the flexor canal is gained by incising the volar antebrachial fascia, the flexor tendons are retracted toward the radial side using a pair of blunt retractors. This provides a space into which the slotted cannula/obturator assembly is inserted. It is believed that this reaction of the flexor tendons places undue traction upon both the ulnar and median neurovascular structures and results in an increased incidence of postoperative median and ulnar nerve neurapraxiae. In addition, the ulnar neurovascular structures are placed at risk by unnecessarily deep dissection into the carpal canal.
Another problem with Dr. Chow's technique is that the proximity of the slotted cannula to the patient's fingers and forearm makes it awkward for the surgeon to manipulate the surgical tools in the cannula during the surgery. Additionally, Dr. Chow's technique employs a five-step cutting process to release the transverse carpal ligament, a process that complicates and prolongs the surgical procedure.
A preliminary report suggesting a simplified procedure for overcoming these problems was made by Drs. Charles T. Resnick and Brent W. Miller in an article entitled Endoscopic Carpal Tunnel Release Using the Subligamentous Two-portal Technique, Contemporary Orthopaedics, 22:3,269-277 (1991).